Server load was high most of the time. I have not made any version 1.5 specific changes on lighttpd configuration. I have found there is some improved configuration options in version 1.5 like linux-aio. I will try this after a day or when the server load get high again so i can notice a load difference after making the changes.

NOTE: The server load decrease was an early assumption. After lighttpd run for some time, server load is high again now.